A lens apparatus of a monitoring camera is attached to the monitoring camera by fastening a mount ring provided at a rear end portion in an optical axis direction of a lens barrel main body to a main body of the monitoring camera (refer to JP-A-2003-255210). Various shapes of the mount rings of the lens apparatus need to be prepared in accordance with a shape, a position of CCD on a side of the camera, a heat radiating characteristic of CCD and the like. Therefore, in a background art, a number of the mount rings having different shapes are prepared, selected in accordance with a specification of a camera and mounted thereto.
Meanwhile, a mount ring of a lens apparatus needs high working accuracy at a portion thereof connected to a lens barrel main body and therefore, there poses a problem that a die in molding the mount ring by a resin is expensive, and fabrication cost is high. Therefore, there poses a problem that cost of a lens barrel is significantly increased by preparing a number of kinds of the mount rings.
A monitoring camera for taking an image day and night provides a picture image by utilizing an infrared ray in taking an image at night, and an infrared ray needs to be cut in taking an image in daytime. Therefore, a lens apparatus of the monitoring camera for taking an image day and night is provided with a filter switching apparatus for arranging an IR cut filter on an optical path, or escaping the IR cut filter from the optical path. Further, the monitoring camera can take an image day and night by arranging the IR cut filter on the optical path in taking an image in daytime and escaping the IR cut filter from the optical path at night by using the filter switching apparatus.
The IR cut filter and the filter switching apparatus are normally attached to a frame or a base seat to be unitized, which is integrated to a lens barrel. For example, according to a lens barrel described in JP-A-2004-347624, an optical filter is slidably supported by a guide frame, a unit of a filter switching apparatus is attached to a base seat, and these units are integrated to between a mount and a fixed cylinder.
However, the lens barrel of JP-A-2004-347624 needs a guide frame or a base seat and therefore, a problem that the apparatus is large-sized is posed. Further, the lens barrel of JP-A-2004-347624 poses a problem that a back focus (a distance from an apex of a final refracting face of a lens to a focusing face) is prolonged by an amount of a thickness of the guide frame or the base seat to deteriorate optical properties.
JP-A-2002-189238 and JP-A-2003-348398 describe a lens barrel in which an optical filter and a filter switching apparatus are integrated to a diaphragm apparatus. According to the lens barrel, the lens barrel can be downsized in an optical axis direction by attaching the optical filter and the filter switching apparatus to a board of the diaphragm apparatus.
However, since the lens barrel of JP-A-2002-189238 and JP-A-2003-348398 is provided with the optical filter and the filter switching apparatus at the diaphragm apparatus, there poses a problem that a thickness of a total of the diaphragm apparatus is increased, movable ranges of optical lenses on front and rear sides of the diaphragm apparatus are restricted, and optical properties are deteriorated.
Further, the lens barrel of JP-A-2002-189238 and JP-A-2003-348398 also poses a problem that when the optical filter is not needed, the total of the diaphragm apparatus needs to be interchanged, and cost is increased.
A lens barrel is connected to a camera by way of a connecting member referred to as lens mount. Normally, the lens barrel and the connecting member are fixed by a screw or the like. The connecting member needs a sufficient mechanical strength for preventing the connecting member from being destructed by unpreparedly strong force or impact in mounting to the camera. Therefore, with regard to the connecting member of the lens barrel, in a background art, there have been proposed various connecting members for increasing the mechanical strength.
For example, JP-A-2000-29116 describes a connecting member in which a portion thereof screwed to be fixed to a lens barrel and a bayonet claw engaged with a camera are reinforced by metal members. According to the connecting member, strengths of a portion screwed to be fixed thereto and the bayonet claw are increased and therefore, the connecting member can be fixed to the lens barrel by a solid fastening force, further, a force of engaging the connecting member of the camera can be increased. Thereby, the connecting member can be prevented from being destructed by an unpreparedly strong force or impact in mounting to the camera.
However, JP-A-2000-29116 poses a problem that warp is brought about at a barrel main body of the lens barrel by fixing the connecting member to the lens barrel by a strong fastening force. Further, by bringing about warp at the barrel main body, there is brought about a drawback that a resistance of sliding an operating ring of a focus ring, a zoom ring or the like and the barrel main body is increased and operability is deteriorated.
Further, JP-A-2000-29116 poses a problem that when the connecting member is screwed to be fixed to the lens barrel by the strong fastening force, a thread ridge of a female screw on a side of the barrel main body is destructed, and the barrel main body per se needs to be interchanged.